I tried 2 different alts in the past and neither fit. That real estate in that location simply sucks and someone in design should be slapped for it. 
That said, I am still with my original alt and find myself replacing my battery every couple of years. Does not help that I have a ton of creature comforts added since inception..... *sigh*
It has been a while since I bothered to browse around and see if there is a higher amp available that has a better fit (or fits at all!). If anyone knows, I'm all ears....
Gary Noonan
'01 S/C VX / '18 Forester XT